Increased resting intracellular calcium modulates NF-κB-dependent inducible nitric-oxide synthase gene expression in dystrophic mdx skeletal myotubes

Abstract

Duchenne muscular dystrophy (DMD) is a genetic disorder caused by dystrophin mutations, characterized by chronic inflammation and severe muscle wasting. Dystrophic muscles exhibit activated immune cell infiltrates, up-regulated inflammatory gene expression, and increased NF-κB activity, but the contribution of the skeletal muscle cell to this process has been unclear. The aim of this work was to study the pathways that contribute to the increased resting calcium ([Ca 2+] rest) observed in mdx myotubes and its possible link with up-regulation of NF-κB and pro-inflammatory gene expression in dystrophic muscle cells. [Ca 2+] rest was higher in mdx than in WT myotubes (308 ± 6 versus 113 ± 2 nM, p < 0.001). In mdx myotubes, both the inhibition of Ca 2+ entry (low Ca 2+ solution, Ca 2+-free solution, and Gd 3+) and blockade of either ryanodine receptors or inositol 1,4,5-trisphosphate receptors reduced [Ca 2+] rest. Basal activity of NF-κB was significantly up-regulated in mdx versus WT myo